Withaferin A is one of the most bioactive phytoconstituents of Withania somnifera, a well-known herb in Ayurvedic medical tradition of India. Due to the lactonal steroid's potential to modulate multiple oncogenic pathways, Withaferin A has gained much attention as a possible anti-neoplastic agent. Systematic research on the evaluation of anticancer activities of withaferin A was started around the 1970s. Since then, a large number of studies have demonstrated the ability of withaferin A to suppress the in vivo growth of various human cancer cells’ xenograft tumors as well as experimentally induced carcinogenesis in different rodent models. It has being reported that withaferin-A reduced the growth of human prostate cancer (PC3) cells tumor xenograft in nude mice by blocking the tumor angiogenesis and inducing intratumoral apoptosis. According to this study, i.p. administration of withaferin-A caused regression of implanted tumor cells by decreasing the expression of angiogenesis marker CD31, inducing the expression of proapoptotic protein Bax, and activating caspase-3 via inhibition of nuclear factor-κB (NF-κB) signaling pathway. In a separate study, intratumoral administration of withaferin-A arrested PC3 cells’ xenograft tumor growth in mice by inducing tumor cell death via upregulation of prostate apoptosis response-4 (Par-4). Anticancer activity of withaferin-A has also being demonstrated for gynecological cancer, melanoma, thyroid, gastrointestinal and other types of cancer. Mechanistic basis of the anticancer effects of withaferin-A includes: (1) reinforcement of cellular antioxidant and/or detoxification system; (2) suppression of inflammatory pathways; (3) selective inhibition of tumor cell proliferation and induction of apoptosis; (4) suppression of tumor angiogenesis; (5) blockade of epithelial-to-mesenchymal transition (EMT), tumor invasion, and metastasis; (6) alteration of tumor cell metabolism; (7) immunomodulation; and (8) eradication of cancer stem cells.

24-Hydroxycalcidiol (24,25-dihydroxy vitamin D3) is a circulating metabolite of vitamin D3. 24,25(OH)2D3 functions by activation of Vitamin D receprtor and promotion of ostecalcin expression, but is less effective than other D3 metabolite, 1alpha,25(OH)2D3. There is conflicting evidence on efffect of 24-hydroxycalcidiol on bone metabolism. In several animal studies it was demonstrated that 24-hydroxycalcidiol was able to stimulate calcification of bone and restore the reduction in bone mineral apposition rate. However, no beneficial effect of 24R,25(OH)2D3 treatment of postmenapausal women on bone mineral density or bone loss and calcium metabolism were observed.

Calanolide A is a new non-nucleoside reverse transcriptase inhibitor (NNRTI) originally extracted from a tropical tree (Calophyllum lanigerum) in the Malaysian rain forest. Viral life-cycle studies indicate that calanolide A acts early in the infection process, similar to the known HIV reverse transcriptase (RT) inhibitor 2', 3'-dideoxycytidine. In enzyme inhibition assays, calanolide A potently and selectively inhibits recombinant HIV type 1 RT but not cellular DNA polymerases or HIV type 2 RT within the concentration range tested. Phase I studies have found that calanolide A is well tolerated. Consequently, it has potential clinical applications in combination with other antiviral drugs to suppress HIV-1 mutants. Nevertheless, the development of calanolide A has been delayed due to its low therapeutic index (range: 16–279), non-ideal antiviral activity, and the complexity of its extraction from plants

Salvinorin A has been reported to be the most potent naturally occurring hallucinogen, with an effective dose in humans in the 200- to the 1,000-μg range when smoked; it has been reported to induce an intense hallucinatory experience in humans, with a typical duration of action being several minutes to an hour or so. Salvinorin A is a highly selective agonist of the kappa-opioid receptor (KOR) with few off-target effects. It is a potent and selective dilator of the cerebral vasculature, exhibits rapid penetration through the blood-brain barrier, has potent anti-inflammatory properties, and has the ability to preserve neurovascular unit integrity. As such, salvinorin A is an ideal compound for the prevention and treatment of cerebral vasospasm following subarachnoid hemorrhage.

Licochalcone A (LicA) is a flavonoid isolated from the famous Chinese medicinal herb Glycyrrhiza uralensis Fisch and has a wide spectrum of pharmacological activities such as anti-oxidant, anti-bacterial, anti-viral, and anti-cancer. However, its pharmacological mechanism is not well defined. The anti-Inflammatory effects of LicA on IL-1β-Stimulated human osteoarthritis chondrocytes was reached by activating Nrf2 signaling pathway. LicA showed anti-proliferative and apoptotic effects in breast cancer cells through regulating Sp1 and apoptosis-related proteins in a dose- and a time-dependent manner. In addition, the chemotherapeutic potential of LicA for treatment of human cervical cancer was achieved by inhibition of PI3K/Akt/mTOR signaling.

MK-8776 (SCH900776) is inhibitor of CHK1. It was tested in clinical trials against acute myeloid leukaemia, solid tumors and lymphoma.

Trichostatin A (TSA) was originally isolated as an antifungal antibiotic along with its fermentation congeners trichostatin B ((TSA)3-Fe) and the D-glucopyranosides trichostatin C and D. TSA inhibits HDAC in the low nanomolar range and is an inducer of histone hyperacetylation, both in vitro and in vivo. It inhibits all class I and II deacetylases to a similar extent in both tumor and non-tumor cells, although HDAC4 is slightly resistant when compared with HDAC1 and HDAC6. Class III HDAC is not affected by TSA. It has been shown that TSA dosedependently inhibits growth and induces apoptosis in a plethora of carcinoma cell lines in vitro. Recently, it was also found that TSA inhibits angiogenesis, which is important for the growth and metastasis of solid tumors, both in vivo and in vitro. In HT-29 colon carcinoma cells, a single dose of TSA induced transient hyperacetylation of histone H4 resulting in the induction of p21WAF1/Cip1 and inhibition of cellular proliferation at both the G1 and G2 phases of the cell cycle. Growth inhibition was associated with decreased cyclin D1 mRNA and cdk6 protein levels and increased cyclin D3 protein and p21WAF1/Cip1 mRNA levels. Cyclin D1 protein, cyclin D3 mRNA, cdk2 and cdk4 remained unaffected. In addition, TSA induced apoptosis by upregulating the expression of the pro-apoptotic genes ID1, ID2 and ID3, whereas the expression of the anti-apoptotic genes BclxL and Hsp27 was decreased In vivo, TSA induces differentiation and shows chemotherapeutic activity against N-methylnitrosureainduced rat mammary cancer without toxic side effects. TSA may also have therapeutic potential for the treatment of a variety of genetic and infectious diseases since silenced, transduced genes are reactivated probably due to structural changes of the chromatin on integrated viral sequences.